THÔNG TIN TÀI LIỆU
Wireless LANs and PANs Outline Electromagnetic spectrum and ISM bands IEEE 802.11 (Wi-Fi) Bluetooth IEEE 802.15.4 Electromagnetic Spectrum RF range Government regulations make specific ranges of the electromagnetic spectrum available for communication A license is required to operate transmission equipment in some parts of the spectrum Some parts are unlicensed ISM Bands Industrial, Scientific, and Medical frequency bands Can operate without FCC licenses Tx output power watt Eliminate cost and time consuming for licenses 915 MHz* 2.45 GHz 5.8 GHz 26 MHz 902 MHz 928 MHz 100 MHz 2.40 GHz 150 MHz 2.50 GHz 5.725 GHz 5.875 GHz * Region only Wireless LANs: IEEE 802.11 (Wi-Fi) IEEE 802.11 IEEE Standard for Wireless LANs Covers both physical and data link layers Wi-Fi Access points Wi-Fi Router WLAN Architectures Basic Service Set (BSS) Extended Service Set (ESS) Basic Service Set (BSS) (Ad hoc mode) (Infrastructure mode) Extended Service Set (ESS) IEEE 802.11 Physical Layer IEEE 802.11 MAC 802.11 802.11a 802.11b 802.11g 802.11n 1-2 Mbps 2.4 GHz FHSS DSSS IR 6-54 Mbps GHz OFDM 1-11 Mbps 2.4 GHz DSSS 6-54 Mbps 2.4 GHz OFDM DSSS 7.2-150 Mbps 2.4, GHz OFDM 10 CSMA/CA With RTS/CTS A B C D RTS CTS NAV Data NAV ACK NAV Network Allocation Vector (Virtual Carrier Sensing) 14 IEEE 802.11 and Wi-Fi IEEE 802.11 provides most of the standards A group of vendors who build wireless equipment formed the Wi-Fi Alliance A non-profit organization that tests and certifies wireless equipment using the 802.11 standards 15 Wireless PANs: Bluetooth Bluetooth Standard Wireless Personal Area Network technology Designed for connecting devices with different functionalities: Telephone, mouse, keyboard, camera, etc Standard IEEE 802.15.1 17 Bluetooth Piconet 18 Bluetooth Scatternet 19 Bluetooth Layers 20 Bluetooth Communication Single slave 21 Bluetooth Communication Multiple slaves 22 Low-Rate Wireless PANs: IEEE 802.15.4 IEEE 802.15.4 IEEE standard for Low-Rate WPAN (LR-WPAN) applications Low-to-medium bit rates Moderate delays without too strict requirements Low cost, low energy consumption Applications Home automation and security systems Smart metering Wireless data collection 24 IEEE 802.15.4 Physical Operating frequency bands Channel Channels 1-10 868.3 MHz 902 MHz 868MHz (20 kbps) 2.4 GHz PHY 2.4 GHz MHz 928 MHz 915 MHz (40 kbps) Channels 11-26 2.4 GHz (250 kbps) MHz 2.4835 GHz 25 IEEE 802.15.4 MAC Single channel at any one time Combines contention-based and schedule-based schemes Asymmetric: nodes can assume different roles 26 IEEE 802.15.4 Devices Full function device (FFD) Any topology Network coordinator capable Talks to any other device Reduced function device (RFD) Limited to star topology Cannot become a network coordinator Talks only to a network coordinator Very simple implementation 27 IEEE 802.15.4 Topologies 28 ... Standard for Wireless LANs Covers both physical and data link layers Wi-Fi Access points Wi-Fi Router WLAN Architectures Basic Service Set (BSS) Extended Service Set (ESS) Basic Service Set (BSS)... 7.2-150 Mbps 2.4, GHz OFDM 10 IEEE 802.11b/g Channels See http://en.wikipedia.org/wiki/List_of _WLAN_ channels 11 IEEE 802.11 MAC Layer PCF – Point Coordination Function (controlled access) DCF
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